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AMBIEN FULL PRESCRIBING INFORMATION INDICATIONS AND USAGE Ambien CR (zolpidem tartrate extended-release tablets) is indicated for the treatment of insomnia characterized by difficulties with sleep onset and/or sleep maintenance (as measured by wake time after sleep onset). The clinical trials performed in support of efficacy were up to 3 weeks (using polysomnography measurement up to 2 weeks in both adult and elderly patients) and 24 weeks (using patient-reported assessment in adult patients only) in duration DOSAGE AND ADMINISTRATION The dose of Ambien CR should be individualized. Dosage in adults The recommended dose of Ambien CR for adults is 12.5 mg once daily immediately before bedtime. The total Ambien CR dose should not exceed 12.5 mg per day. Special populations Elderly or debilitated patients may be especially sensitive to the effects of zolpidem tartrate. Patients with hepatic insufficiency do not clear the drug as rapidly as normals. The recommended dose of Ambien CR in both of these patient populations is 6.25 mg once daily immediately before bedtime Use with CNS depressants Dosage adjustments may be necessary when Ambien CR is combined with other CNS depressant drugs because of the potentially additive effects Administration Ambien CR extended-release tablets should be swallowed whole, and not be divided, crushed, or chewed. The effect of Ambien CR may be slowed by ingestion with or immediately after a meal. DOSAGE FORMS AND STRENGTHS Ambien CR is available as extended-release tablets containing 6.25 mg or 12.5 mg of zolpidem tartrate for oral administration. Tablets are not scored. Ambien CR 6.25 mg tablets are pink, round, bi-convex, and debossed with A~ on one side. Ambien CR 12.5 mg tablets are blue, round, bi-convex, and debossed with A~ on one side. CONTRAINDICATIONS Ambien CR is contraindicated in patients with known hypersensitivity to zolpidem tartrate or to any of the inactive ingredients in the formulation. Observed reactions include anaphylaxis and angioedema WARNINGS AND PRECAUTIONS Need to evaluate for co-morbid diagnoses Because sleep disturbances may be the presenting manifestation of a physical and/or psychiatric disorder, symptomatic treatment of insomnia should be initiated only after a careful evaluation of the patient. The failure of insomnia to remit after 7 to 10 days of treatment may indicate the presence of a primary psychiatric and/or medical illness that should be evaluated. Worsening of insomnia or the emergence of new thinking or behavior abnormalities may be the consequence of an unrecognized psychiatric or physical disorder. Such findings have emerged during the course of treatment with sedative/hypnotic drugs, including zolpidem. Severe anaphylactic and anaphylactoid reactions Rare cases of angioedema involving the tongue, glottis or larynx have been reported in
patients after taking the first or subsequent doses of sedative-hypnotics, including zolpidem. Some patients have had additional symptoms such as dyspnea, throat closing or nausea and vomiting that suggest anaphylaxis. Some patients have required medical therapy in the emergency department. If angioedema involves the throat, glottis or larynx, airway obstruction may occur and be fatal. Patients who develop angioedema after treatment with zolpidem should not be rechallenged with the drug. Abnormal thinking and behavioral changes A variety of abnormal thinking and behavior changes have been reported to occur in association with the use of sedative/hypnotics. Some of these changes may be characterized by decreased inhibition (e.g. aggressiveness and extroversion that seemed out of character), similar to effects produced by alcohol and other CNS depressants. Visual and auditory hallucinations have been reported as well as behavioral changes such as bizarre behavior, agitation and depersonalization. In controlled trials, <1% of adults with insomnia who received zolpidem reported hallucinations. In a clinical trial, 7.4% of pediatric patients with insomnia associated with attention-deficit/hyperactivity disorder (ADHD), who received zolpidem reported hallucinations [ Complex behaviors such as "sleep-driving" (i.e., driving while not fully awake after ingestion of a sedative-hypnotic, with amnesia for the event) have been reported with sedative-hypnotics, including zolpidem. These events can occur in sedative-hypnotic- naive as well as in sedative-hypnotic-experienced persons. Although behaviors such as "sleep-driving" may occur with Ambien CR alone at therapeutic doses, the use of alcohol and other CNS depressants with Ambien CR appears to increase the risk of such behaviors, as does the use of Ambien CR at doses exceeding the maximum recommended dose. Due to the risk to the patient and the community, discontinuation of Ambien CR should be strongly considered for patients who report a "sleep-driving" episode. Other complex behaviors (e.g., preparing and eating food, making phone calls, or having sex) have been reported in patients who are not fully awake after taking a sedative-hypnotic. As with "sleep-driving", patients usually do not remember these events. Amnesia, anxiety and other neuro-psychiatric symptoms may occur unpredictably. In primarily depressed patients, worsening of depression, including suicidal thoughts and actions (including completed suicides), have been reported in association with the use of sedative/hypnotics. It can rarely be determined with certainty whether a particular instance of the abnormal behaviors listed above is drug induced, spontaneous in origin, or a result of an underlying psychiatric or physical disorder. Nonetheless, the emergence of any new behavioral sign or symptom of concern requires careful and immediate evaluation. Withdrawal effects Following the rapid dose decrease or abrupt discontinuation of sedative/hypnotics, there have been reports of signs and symptoms similar to those associated with withdrawal from other CNS-depressant drugs [ CNS depressant effects Ambien CR, like other sedative/hypnotic drugs, has CNS-depressant effects. Due to the rapid onset of action, Ambien CR should only be taken immediately prior to going to bed. Patients should be cautioned against engaging in hazardous occupations requiring complete mental alertness or motor coordination such as operating machinery or driving a motor vehicle after ingesting the drug, including potential impairment of the performance of such activities that may occur the day following ingestion of Ambien CR. Ambien CR showed additive effects when combined with alcohol and should not be taken with alcohol. Patients should also be cautioned about possible combined effects with other CNS-depressant drugs. Dosage adjustments may be necessary when Ambien CR is administered with such agents because of the potentially additive effects. Special populations Use in the elderly and/or debilitated patients: Impaired motor and/or cognitive performance after repeated exposure or unusual sensitivity to sedative/hypnotic drugs is a concern in the treatment of elderly and/or debilitated patients. Therefore, the recommended Ambien CR dosage is 6.25 mg in such patients to decrease the possibility of side effects. These patients should be closely monitored. Use in patients with concomitant illness: Clinical experience with Ambien CR (zolpidem tartrate) in patients with concomitant systemic illness is limited. Caution is advisable in using Ambien CR in patients with diseases or conditions that could affect metabolism or hemodynamic responses. Although studies did not reveal respiratory depressant effects at hypnotic doses of zolpidem in normals or in patients with mild to moderate chronic obstructive pulmonary disease (COPD), a reduction in the Total Arousal Index together with a reduction in lowest oxygen saturation and increase in the times of oxygen desaturation below 80% and 90% was observed in patients with mild-to-moderate sleep apnea when treated with an immediate-release formulation of zolpidem tartrate (10 mg) when compared to placebo. Since sedative/hypnotics have the capacity to depress respiratory drive, precautions should be taken if Ambien CR is prescribed to patients with compromised respiratory function. Post-marketing reports of respiratory insufficiency, most of which involved patients with pre-existing respiratory impairment, have been received. Ambien CR should be used with caution in patients with sleep apnea syndrome or myasthenia gravis. Data in end-stage renal failure patients repeatedly treated with an immediate-release formulation of zolpidem tartrate (10 mg) did not demonstrate drug accumulation or alterations in pharmacokinetic parameters. No dosage adjustment in renally impaired patients is required; however, these patients should be closely monitored A study in subjects with hepatic impairment did reveal prolonged elimination in this group; therefore, treatment should be initiated with Ambien CR 6.25 mg in patients with hepatic compromise, and they should be closely monitored Use in patients with depression: As with other sedative/hypnotic drugs, Ambien CR should be administered with caution to patients exhibiting signs or symptoms of depression. Suicidal tendencies may be present in such patients and protective measures may be required. Intentional overdosage is more common in this group of patients; therefore, the least amount of drug that is feasible should be prescribed for the patient at any one time. Use in pediatric patients: Safety and effectiveness of zolpidem has not been established in pediatric patients. In an 8-week study in pediatric patients (aged 6–17 years) with insomnia associated with ADHD given an immediate-release oral solution of zolpidem tartrate, zolpidem did not decrease sleep latency compared to placebo. Hallucinations were reported in 7.4% of the pediatric patients who received zolpidem; none of the pediatric patients who received placebo reported hallucinations ADVERSE REACTIONS The following serious adverse reactions are discussed in greater detail in other sections of the labeling: ¥Serious anaphylactic and anaphylactoid reactions ¥Abnormal thinking, behavior changes, and complex behaviors ¥Withdrawal effects ¥CNS-depressant effects Clinical trials experience Associated with discontinuation of treatment: In 3-week clinical trials in adults and elderly patients (> 65 years), 3.5% (7/201) patients receiving Ambien CR 6.25 or 12.5 mg discontinued treatment due to an adverse reaction as compared to 0.9% (2/216) of patients on placebo. The reaction most commonly associated with discontinuation in patients treated with Ambien CR was somnolence (1%). In a 6-month study in adult patients (18–64 years of age), 8.5% (57/669) of patients receiving Ambien CR 12.5 mg as compared to 4.6% on placebo (16/349) discontinued treatment due to an adverse reaction. Reactions most commonly associated with discontinuation of Ambien CR included anxiety (anxiety, restlessness or agitation) reported in 1.5% (10/669) of patients as compared to 0.3% (1/349) of patients on placebo, and depression (depression, major depression or depressed mood) reported in 1.5% (10/669) of patients as compared to 0.3% (1/349) of patients on placebo. Data from a clinical study in which selective serotonin reuptake inhibitor- (SSRI-) treated patients were given zolpidem revealed that four of the seven discontinuations during double-blind treatment with zolpidem (n=95) were associated with impaired concentration, continuing or aggravated depression, and manic reaction; one patient treated with placebo (n =97) was discontinued after an attempted suicide. Most commonly observed adverse reactions in controlled trials: During treatment with Ambien CR in adults and elderly at daily doses of 12.5 mg and 6.25 mg, respectively, each for three weeks, the most commonly observed adverse reactions associated with the use of Ambien CR were headache, next-day somnolence, and dizziness. In the 6-month trial evaluating Ambien CR 12.5 mg, the adverse reaction profile was consistent with that reported in short-term trials, except for a higher incidence of anxiety (6.3% for Ambien CR versus 2.6% for placebo). Adverse reactions observed at an incidence of ≥1% in controlled trials: The following tables enumerate treatment-emergent adverse reaction frequencies that were observed at an incidence equal to 1% or greater among patients with insomnia who received Ambien CR in placebo-controlled trials. Events reported by investigators were classified utilizing the MedDRA dictionary for the purpose of establishing event frequencies. The prescriber should be aware that these figures cannot be used to predict the incidence of side effects in the course of usual medical practice, in which patient characteristics and other factors differ from those that prevailed in these clinical trials. Similarly, the cited frequencies cannot be compared with figures obtained from other clinical investigators involving related drug products and uses, since each group of drug trials is conducted under a different set of conditions. However, the cited figures provide the physician with a basis for estimating the relative contribution of drug and nondrug factors to the incidence of side effects in the population studied. The following tables were derived from results of two placebo-controlled efficacy trials involving Ambien CR. These trials involved patients with primary insomnia who were treated for 3 weeks with Ambien CR at doses of 12.5 mg (Table 1) or 6.25 mg (Table 2), respectively. The tables include only adverse reactions occurring at an incidence of at least 1% for Ambien CR patients and with an incidence greater than that seen in the placebo patients. Table 1. Incidences of Treatment-Emergent Adverse Reactions in a 3-Week Placebo-Controlled Clinical Trial in Adults (percentage of patients reporting) Body System/Adverse Reaction * Ambien CR 12.5 mg Placebo (N = 102) (N = 110) Infections and infestations Influenza 3 0 Gastroenteritis 1 0 Labyrinthitis 1 0 Metabolism and nutrition disorders Appetite disorder 1 0 Psychiatric disorders Hallucinations 4 0 Disorientation 3 2 Anxiety 2 0 Depression 2 0 Psychomotor retardation 2 0 Binge eating 1 0 Depersonalization 1 0 Disinhibition 1 0 Euphoric mood 1 0 Mood swings 1 0 Stress symptoms 1 0 Nervous system disorders Headache 19 16 Somnolence 15 2 Dizziness 12 5 Memory disorders 3 0 Balance disorder 2 0 Disturbance in attention 2 0 Hypoesthesia 2 1 Ataxia 1 0 Paresthesia 1 0 Eye disorders Visual disturbance 3 0 Eye redness 2 0 Vision blurred 2 1 Altered visual depth perception 1 0 Asthenopia 1 0 Ear and labyrinth disorders Vertigo 2 0 Tinnitus 1 0 Respiratory, thoracic and mediastinal disorders Throat irritation 1 0 Gastrointestinal disorders Nausea 7 4 Constipation 2 0 Abdominal discomfort 1 0 Abdominal tenderness 1 0 Frequent bowel movements 1 0 Gastroesophageal reflux disease 1 0 Vomiting 1 0 Skin and subcutaneous tissue disorders Rash 1 0 Skin wrinkling 1 0 Urticaria 1 0 Musculoskeletal and connective tissue disorders Back pain 4 3 Myalgia 4 0 Neck pain 1 0 Reproductive system and breast disorders Menorrhagia 1 0 General disorders and administration site conditions Fatigue 3 2 Asthenia 1 0 Chest discomfort 1 0 Investigations Blood pressure increased 1 0 Body temperature increased 1 0 Injury, poisoning and procedural complications Contusion 1 0 Social circumstances Exposure to poisonous plant 1 0 * Reactions reported by at least 1% of patients treated with Ambien CR and at greater frequency than in the placebo group. Hallucinations included hallucinations NOS as well as visual and hypnogogic hallucinations. Memory disorders include: memory impairment, amnesia, anterograde amnesia. Table 2. Incidences of Treatment-Emergent Adverse Reactions in a 3-Week Placebo-Controlled Clinical Trial in Elderly (percentage of patients reporting) Body System/Adverse Reaction * Ambien CR Placebo 6.25 mg (N=99) (N=106) Infections and infestations Nasopharyngitis 6 4 Lower respiratory tract infection 1 0 Otitis externa 1 0 Upper respiratory tract infection 1 0 Psychiatric disorders Anxiety 3 2 Psychomotor retardation 2 0 Apathy 1 0 Depressed mood 1 0 Nervous system disorders Headache 14 11 Dizziness 8 3 Somnolence 6 5 Burning sensation 1 0 Dizziness postural 1 0 Memory disorders 1 0 Muscle contractions involuntary 1 0 Paresthesia 1 0 Tremor 1 0 Cardiac disorders Palpitations 2 0 Respiratory, thoracic and mediastinal disorders Dry throat 1 0 Gastrointestinal disorders Flatulence 1 0 Vomiting 1 0 Skin and subcutaneous tissue disorders Rash 1 0 Urticaria 1 0 Musculoskeletal and connective tissue disorders Arthralgia 2 0 Muscle cramp 2 1 Neck pain 2 0 Renal and urinary disorders Dysuria 1 0 Reproductive system and breast disorders Vulvovaginal dryness 1 0 General disorders and administration site conditions Influenza like illness 1 0 Pyrexia 1 0 Injury, poisoning and procedural complications Neck injury 1 0 * Reactions reported by at least 1% of patients treated with Ambien CR and at greater frequency than in the placebo group. Memory disorders include: memory impairment, amnesia, anterograde amnesia. Dose relationship for adverse reactions: There is evidence from dose comparison trials suggesting a dose relationship for many of the adverse reactions associated with zolpidem use, particularly for certain CNS and gastrointestinal adverse events. DRUG INTERACTIONS CNS-active drugs Since the systematic evaluations of zolpidem in combination with other CNS-active drugs have been limited, careful consideration should be given to the pharmacology of any CNS-active drug to be used with zolpidem. Any drug with CNS- depressant effects could potentially enhance the CNS-depressant effects of zolpidem. An immediate-release formulation of zolpidem tartrate was evaluated in healthy subjects in single-dose interaction studies for several CNS drugs. Imipramine in combination with zolpidem produced no pharmacokinetic interaction other than a 20% decrease in peak levels of imipramine, but there was an additive effect of decreased alertness. Similarly, chlorpromazine in combination with zolpidem produced no pharmacokinetic interaction, but there was an additive effect of decreased alertness and psychomotor performance. A study involving haloperidol and zolpidem revealed no effect of haloperidol on the pharmacokinetics or pharmacodynamics of zolpidem. The lack of a drug interaction following single-dose administration does not predict a lack following chronic administration. An additive effect on psychomotor performance between alcohol and zolpidem was demonstrated A single-dose interaction study with zolpidem 10 mg and fluoxetine 20 mg at steady-state levels in male volunteers did not demonstrate any clinically significant pharmacokinetic or pharmacodynamic interactions. When multiple doses of zolpidem and fluoxetine at steady-state concentrations were evaluated in healthy females, the only significant change was a 17% increase in the zolpidem half-life. There was no evidence of an additive effect in psychomotor performance. Following five consecutive nightly doses of zolpidem 10 mg in the presence of sertraline 50 mg (17 consecutive daily doses, at 7:00 am, in healthy female volunteers), zolpidem Cmax was significantly higher (43%) and Tmax was significantly decreased (53%). Pharmacokinetics of sertraline and N-desmethylsertraline were unaffected by zolpidem. Drugs that affect drug metabolism via cytochrome P450 Some compounds known to inhibit CYP3A may increase exposure to zolpidem. The effect of inhibitors of other P450 enzymes has not been carefully evaluated. A randomized, double-blind, crossover interaction study in ten healthy volunteers between itraconazole (200 mg once daily for 4 days) and a single dose of zolpidem (10 mg) given 5 hours after the last dose of itraconazole resulted in a 34% increase in AUC0–∞ of zolpidem. There were no significant pharmacodynamic effects of zolpidem on subjective drowsiness, postural sway, or psychomotor performance. A randomized, placebo-controlled, crossover interaction study in eight healthy female subjects between five consecutive daily doses of rifampin (600 mg) and a single dose of an immediate-release formulation of zolpidem tartrate (20 mg) given 17 hours after the last dose of rifampin showed significant reductions of the AUC (–73%), Cmax (–58%), and T1/2 (–36%) of zolpidem together with significant reductions in the pharmacodynamic effects of zolpidem. A randomized double-blind crossover interaction study in twelve healthy subjects showed that co-administration of a single 5 mg dose of immediate-release zolpidem tartrate with ketoconazole, a potent CYP3A4 inhibitor, given as 200 mg twice daily for 2 days increased Cmax of zolpidem by a factor of 1.3 and increased the total AUC of zolpidem by a factor of 1.7 compared to zolpidem alone and prolonged the elimination half-life by approximately 30% along with an increase in the pharmacodynamic effects of zolpidem. Caution should be used when ketoconazole is given with zolpidem and consideration should be given to using a lower dose of zolpidem when ketoconazole and zolpidem are given together. Patients should be advised that use of Ambien CR with ketoconazole may enhance the sedative effects. Other drugs with no interaction with zolpidem A study involving cimetidine/zolpidem and ranitidine/zolpidem combinations revealed no effect of either drug on the pharmacokinetics or pharmacodynamics of zolpidem. Zolpidem had no effect on digoxin pharmacokinetics and did not affect prothrombin time when given with warfarin in normal subjects. Drug-laboratory test interactions Zolpidem is not known to interfere with commonly employed clinical laboratory tests. In addition, clinical data indicate that zolpidem does not cross-react with benzodiazepines, opiates, barbiturates, cocaine, cannabinoids, or amphetamines in two standard urine drug screens. USE IN SPECIFIC POPULATIONS Pregnancy Pregnancy Category C There are no adequate and well-controlled studies of Ambien CR in pregnant women. Ambien CR should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Administration of zolpidem to pregnant rats and rabbits resulted in adverse effects on offspring development at doses greater than the Ambien CR maximum recommended human dose (MRHD) of 12.5 mg/day (approximately 10 mg/day zolpidem base); however, teratogenicity was not observed. When zolpidem was administered at oral doses of 4, 20, and 100 mg base/kg (approximately 4, 20 and 100 times the MRHD on a mg/m2 basis) to pregnant rats during the period of organogenesis, dose-related decreases in fetal skull ossification occurred at all but the lowest dose, which is approximately 4 times the MRHD on a mg/m2 basis. In rabbits treated during organogenesis with zolpidem at oral doses of 1, 4, and 16 mg base/kg (approximately 2, 8 and 30 times the MRHD on a mg/m2 basis), increased embryo-fetal death and incomplete fetal skeletal ossification occurred at the highest dose. The no-effect dose for embryo-fetal toxicity in rabbits is approximately 8 times the MRHD on a mg/m2 basis. Administration of zolpidem to rats at oral doses of 4, 20, and 100 mg base/kg (approximately 4, 20 and 100 times the MRHD on a mg/m2 basis) during the latter part of pregnancy and throughout lactation produced decreased offspring growth and survival at all but the lowest dose, which is approximately 4 times the MRHD on a mg/m2 basis. Neonatal complications Studies in children to assess the effects of prenatal exposure to zolpidem have not been conducted; however, cases of severe neonatal respiratory depression have been reported when zolpidem was used at the end of pregnancy, especially when taken with other CNS depressants. Children born to mothers taking sedative-hypnotic drugs may be at some risk for withdrawal symptoms during the postnatal period. Neonatal flaccidity has been reported in infants born to mothers who received sedative-hypnotic drugs during pregnancy. Labor and delivery Ambien CR has no established use in labor and delivery Nursing mothers Zolpidem is excreted in human milk. Studies in lactating mothers indicate that the half-life of zolpidem is similar to that in non- lactating women (2.6 ± 0.3 hr). The effect of zolpidem on the nursing infant is not known. Caution should be exercised when Ambien CR is administered to a nursing woman. Pediatric use Safety and effectiveness of zolpidem have not been established in pediatric patients. In an 8-week controlled study, 201 pediatric patients (aged 6–17 years) with insomnia associated with attention- deficit/hyperactivity disorder (90% of the patients were using psychoanaleptics), were treated with an oral solution of zolpidem (n=136), or placebo (n = 65). Zolpidem did not significantly decrease latency to persistent sleep, compared to placebo, as measured by polysomnography after 4 weeks of treatment. Psychiatric and nervous system disorders comprised the most frequent (> 5%) treatment emergent adverse reactions observed with zolpidem versus placebo and included dizziness (23.5% vs. 1.5%), headache (12.5% vs. 9.2%), and hallucinations (7.4% vs. 0%). Ten patients on zolpidem (7.4%) discontinued treatment due to an adverse reaction. FDA has not required pediatric studies of Ambien CR in the pediatric population based on these efficacy and safety findings. Geriatric use A total of 99 elderly (≥ 65 years of age) received daily doses of 6.25 mg Ambien CR in a 3-week placebo-controlled study. The adverse reaction profile of Ambien CR 6.25 mg in this population was similar to that of Ambien CR 12.5 mg in younger adults (≤ 64 years of age). Dizziness was reported in 8% of Ambien CR-treated patients compared with 3% of those treated with placebo. The dose of Ambien CR in elderly patients is 6.25 mg to minimize adverse effects related to impaired motor and/or cognitive performance and unusual sensitivity to sedative/hypnotic drugs DRUG ABUSE AND DEPENDENCE Controlled substance Zolpidem tartrate is classified as a Schedule IV controlled substance by federal regulation. Abuse Abuse and addiction are separate and distinct from physical dependence and tolerance. Abuse is characterized by misuse of the drug for non-medical purposes, often in combination with other psychoactive substances. Tolerance is a state of adaptation in which exposure to a drug induces changes that result in a diminution of one or more of the drug effects over time. Tolerance may occur to both desired and undesired effects of drugs and may develop at different rates for different effects. Addiction is a primary, chronic, neurobiological disease with genetic, psychosocial, and environmental factors influencing its development and manifestations. It is characterized by behaviors that include one or more of the following: impaired control over drug use, compulsive use, continued use despite harm, and craving. Drug addiction is a treatable disease, using a multidisciplinary approach, but relapse is common. Studies of abuse potential in former drug abusers found that the effects of single doses of zolpidem tartrate 40 mg were similar, but not identical, to diazepam 20 mg, while zolpidem tartrate 10 mg effects were difficult to distinguish from placebo. Because persons with a history of addiction to, or abuse of, drugs or alcohol are at increased risk for misuse, abuse and addiction of zolpidem, they should be monitored carefully when receiving zolpidem or any other hypnotic. Dependence Physical dependence is a state of adaptation that is manifested by a specific withdrawal syndrome that can be produced by abrupt cessation, rapid dose reduction, decreasing blood level of the drug, and/or administration of an antagonist. Sedative/hypnotics have produced withdrawal signs and symptoms following abrupt discontinuation. These reported symptoms range from mild dysphoria and insomnia to a withdrawal syndrome that may include abdominal and muscle cramps, vomiting, sweating, tremors, and convulsions. The following adverse events, which are considered to meet the DSM-III-R criteria for uncomplicated sedative/hypnotic withdrawal, were reported during U.S. clinical trials following placebo substitution occurring within 48 hours following last zolpidem treatment: fatigue, nausea, flushing, lightheadedness, uncontrolled crying, emesis, stomach cramps, panic attack, nervousness, and abdominal discomfort. These reported adverse events occurred at an incidence of 1% or less. However, available data cannot provide a reliable estimate of the incidence, if any, of dependence during treatment at recommended doses. Post-marketing reports of abuse, dependence and withdrawal have been received. OVERDOSAGE Signs and symptoms In postmarketing experience of overdose with zolpidem tartrate alone, or in combination with CNS-depressant agents, impairment of consciousness ranging from somnolence to coma, cardiovascular and/or respiratory compromise and fatal outcomes have been reported. Recommended treatment General symptomatic and supportive measures should be used along with immediate gastric lavage where appropriate. Intravenous fluids should be administered as needed. Zolpidem's sedative hypnotic effect was shown to be reduced by flumazenil and therefore may be useful; however, flumazenil administration may contribute to the appearance of neurological symptoms (convulsions). As in all cases of drug overdose, respiration, pulse, blood pressure, and other appropriate signs should be monitored and general supportive measures employed. Hypotension and CNS depression should be monitored and treated by appropriate medical intervention. Sedating drugs should be withheld following zolpidem overdosage, even if excitation occurs. The value of dialysis in the treatment of overdosage has not been determined, although hemodialysis studies in patients with renal failure receiving therapeutic doses have demonstrated that zolpidem is not dialyzable. As with the management of all overdosage, the possibility of multiple drug ingestion should be considered. The physician may wish to consider contacting a poison control center for up-to-date information on the management of hypnotic drug product overdosage. DESCRIPTION Ambien CR contains zolpidem tartrate, a non-benzodiazepine hypnotic of the imidazopyridine class. Ambien CR (zolpidem tartrate extended-release tablets) is available in 6.25 mg and 12.5 mg strength tablets for oral administration. Chemically, zolpidem is N,N,6-trimethyl-2-p-tolylimidazo[1,2-a] pyridine-3-acetamide L-(+)-tartrate (2:1). It has the following structure: Zolpidem tartrate is a white to off-white crystalline powder that is sparingly soluble in water, alcohol, and propylene glycol. It has a molecular weight of 764.88. Ambien CR consists of a coated two-layer tablet: one layer that releases its drug content immediately and another layer that allows a slower release of additional drug content. The 6.25 mg Ambien CR tablet contains the following inactive ingredients: colloidal silicon dioxide, hypromellose, lactose monohydrate, magnesium stearate, microcrystalline cellulose, polyethylene glycol, potassium bitartrate, red ferric oxide, sodium starch glycolate, and titanium dioxide. The 12.5 mg Ambien CR tablet contains the following inactive ingredients: colloidal silicon dioxide, FD&C Blue #2, hypromellose, lactose monohydrate, magnesium stearate, microcrystalline cellulose, polyethylene glycol, potassium bitartrate, sodium starch glycolate, titanium dioxide, and yellow ferric oxide. CLINICAL PHARMACOLOGY Mechanism of action Zolpidem, the active moiety of zolpidem tartrate, is a hypnotic agent with a chemical structure unrelated to benzodiazepines, barbiturates, or other drugs with known hypnotic properties. It interacts with a GABA-BZ receptor complex and shares some of the pharmacological properties of the benzodiazepines. In contrast to the benzodiazepines, which non-selectively bind to and activate all BZ receptor subtypes, zolpidem in vitro binds the BZ1 receptor preferentially with a high affinity ratio of the α1/α5 subunits. This selective binding of zolpidem on the BZ1 receptor is not absolute, but it may explain the relative absence of myorelaxant and anticonvulsant effects in animal studies as well as the preservation of deep sleep (stages 3 and 4) in human studies of zolpidem tartrate at hypnotic doses. Pharmacokinetics Ambien CR exhibits biphasic absorption characteristics, which results in rapid initial absorption from the gastrointestinal tract similar to zolpidem tartrate immediate-release, then provides extended plasma concentrations beyond three hours after administration. A study in 24 healthy male subjects was conducted to compare mean zolpidem plasma concentration-time profiles obtained after single oral administration of Ambien CR 12.5 mg and of an immediate-release formulation of zolpidem tartrate (10 mg). The terminal elimination half-life observed with Ambien CR (12.5 mg) was similar to that obtained with immediate-release zolpidem tartrate (10 mg). The mean plasma concentration-time profiles are shown in Figure 1. Figure 1: Mean plasma concentration-time profiles for Ambien CR (12.5 mg) and immediate-release zolpidem tartrate (10 mg) In adult and elderly patients treated with Ambien CR, there was no evidence of accumulation after repeated once-daily dosing for up to two weeks. Absorption: Following administration of Ambien CR, administered as a single 12.5 mg dose in healthy male adult subjects, the mean peak concentration (Cmax) of zolpidem was 134 ng/mL (range: 68.9 to 197 ng/ml) occurring at a median time (Tmax) of 1.5 hours. The mean AUC of zolpidem was 740 ng∙hr/mL (range: 295 to 1359 ng∙hr/mL). A food-effect study in 45 healthy subjects compared the pharmacokinetics of Ambien CR 12.5 mg when administered while fasting or within 30 minutes after a meal. Results demonstrated that with food, mean AUC and Cmax were decreased by 23% and 30%, respectively, while median Tmax was increased from 2 hours to 4 hours. The half-life was not changed. These results suggest that, for faster sleep onset, Ambien CR should not be administered with or immediately after a meal. Distribution: Total protein binding was found to be 92.5 ± 0.1% and remained constant, independent of concentration between 40 and 790 ng/mL. Metabolism: Zolpidem is converted to inactive metabolites that are eliminated primarily by renal excretion. Elimination: When Ambien CR was administered as a single 12.5 mg dose in healthy male adult subjects, the mean zolpidem elimination half- life was 2.8 hours (range: 1.62 to 4.05 hr). Special Populations Elderly: In 24 elderly (≥ 65 years) healthy subjects administered a single 6.25 mg dose of Ambien CR, the mean peak concentration (Cmax) of zolpidem was 70.6 (range: 35.0 to 161) ng/mL occurring at a median time (Tmax) of 2.0 hours. The mean AUC of zolpidem was 413 ng∙hr/mL (range: 124 to 1190 ng∙hr/mL) and the mean elimination half-life was 2.9 hours (range: 1.59 to 5.50 hours). Hepatic Impairment: Ambien CR was not studied in patients with hepatic impairment. The pharmacokinetics of an immediate-release formulation of zolpidem tartrate in eight patients with chronic hepatic insufficiency were compared to results in healthy subjects. Following a single 20-mg oral zolpidem tartrate dose, mean Cmax and AUC were found to be two times (250 vs. 499 ng/mL) and five times (788 vs. 4,203 ng∙hr/mL) higher, respectively, in hepatically compromised patients. Tmax did not change. The mean half-life in cirrhotic patients of 9.9 hr (range: 4.1 to 25.8 hr) was greater than that observed in normal subjects of 2.2 hr (range: 1.6 to 2.4 hr). Dosing should be modified accordingly in patients with hepatic insufficiency Renal Impairment: Ambien CR was not studied in patients with renal impairment. The pharmacokinetics of an immediate-release formulation of zolpidem tartrate were studied in 11 patients with end-stage renal failure (mean ClCr = 6.5 ± 1.5 mL/min) undergoing hemodialysis three times a week, who were dosed with zolpidem tartrate 10 mg orally each day for 14 or 21 days. No statistically significant differences were observed for Cmax, Tmax, half-life, and AUC between the first and last day of drug administration when baseline concentration adjustments were made. On day 1, Cmax was 172 ± 29 ng/mL (range: 46 to 344 ng/mL). After repeated dosing for 14 or 21 days, Cmax was 203 ± 32 ng/mL (range: 28 to 316 ng/mL). On day 1, Tmax was 1.7 ± 0.3 hr (range: 0.5 to 3.0 hr); after repeated dosing Tmax was 0.8 ± 0.2 hr (range: 0.5 to 2.0 hr). This variation is accounted for by noting that last-day serum sampling began 10 hours after the previous dose, rather than after 24 hours. This resulted in residual drug concentration and a shorter period to reach maximal serum concentration. On day 1, T1/2 was 2.4 ± 0.4 hr (range: 0.4 to 5.1 hr). After repeated dosing, T1/2 was 2.5 ± 0.4 hr (range: 0.7 to 4.2 hr). AUC was 796 ± 159 ng∙hr/mL after the first dose and 818 ± 170 ng∙hr/mL after repeated dosing. Zolpidem was not hemodialyzable. No accumulation of unchanged drug appeared after 14 or 21 days. Zolpidem pharmacokinetics were not significantly different in renally-impaired patients. No dosage adjustment is necessary in patients with compromised renal function. However, as a general precaution, these patients should be closely monitored. NONCLINICAL TOXICOLOGY Carcinogenesis, mutagenesis, impairment of fertility Carcinogenesis: Zolpidem was administered to mice and rats for 2 years at dietary dosages of 4, 18, and 80 mg base/kg. In mice, these doses are approximately 2, 9, and 40 times the maximum recommended human dose (MRHD) of 12.5 mg/day (10 mg zolpidem base) on mg/m2 basis. In rats, these doses are approximately 4, 18, and 80 times the MRHD on a mg/m2 basis. No evidence of carcinogenic potential was observed in mice. In rats, renal tumors (lipoma, liposarcoma) were seen at the mid- and high doses. Mutagenesis: Zolpidem was negative in in vitro (bacterial reverse mutation, mouse lymphoma, and chromosomal aberration) and in vivo (mouse micronucleus) genetic toxicology assays. Impairment of fertility: Oral administration of zolpidem (doses of 4, 20, and 100 mg base/kg or approximately 4, 20, and 100 times the MRHD on a mg/m2 basis) to rats prior to and during mating, and continuing in females through postpartum day 25, resulted in irregular estrus cycles and prolonged precoital intervals. The no-effect dose for these findings is approximately 20 times the MRHD on a mg/m2 basis. There was no impairment of fertility at any dose tested.